SEMICONDUCTOR DEVICE AND ELECTRONIC SYSTEM INCLUDING THE SAME

A semiconductor device includes gate layers and lower insulating layers that are alternately stacked on an upper surface of a substrate, a channel structure passing through the gate layers and the lower insulating layers and extending in a vertical direction, a string select gate layer disposed on the channel structure, a string select channel structure passing through the string select gate layer and extending in the vertical direction, and a contact pad disposed in a space between the channel structure and the string select channel structure and connecting the channel structure to the string select channel structure. A lower surface of the contact pad contacts the channel structure and an upper surface of the contact pad contacts the string select channel structure. A first width of the lower surface of the contact pad is greater than a second width of a central portion of the contact pad. A third width of the upper surface of the contact pad is greater than the second width of the central portion of the contact pad.